Instrument for enciphering and deciphering



June 4, 1935. N. A. SMITH 2,003,812

Y INSTRUMENT FOR ENCIPHERING AND DECIPHERING Filed Jan.` 5, 1934 Flai lbM /1 E.

then being repositioned.

In enciphering a message the used in the following manner. The device isfirst adjusted so that for a zero setting of the slide member 3 therotatable member k5 isf-positioned to show the key letter through thewindow I I, such key letter being known to the recipient;V Assume thekey letterrto be S which corresponds to the settingshownein thedrawings.

An arrangement' of letters or words comprising thecode sentence, which`isalso 'known to Athe recipient, is written upon va pad or elsewhereand the message is written letter for letter beneath the code sentence.lsupposerthe start ofthe code sentence to be Adelaide and the start ofthe/messageto be New This `is written upon the pad thus l j .AdelaideNew The slide member 3vis now moved until the N upon it comes adjacentthe A onthe base member` I.v The movement of the slide member rotates`the rotatable member 5 [toshow F through the window I I. This is therst letter of the Cypher.

'I'hejslide member 3. is next Vmoved until the E upon it comes adjacent.the D on the base c member I. This will'be found to give .the'letter Ras the second letter ofthe cypher.

' The slide member 3 is `then moved to bring the W, upon itadjacent theE on the fbase member, whereuponthe A will appearv in the window II asthe third letter of thecypher.

' The-start of the 'Cypher which is transmitted tothe recipient is thusliltr-Yl ner. l l n c rIhe instrument is adjusted by the recipient'sothat for the zero setting .of the slide Ymember 3 the key letter S(which isY knownfto him) appears in the ywindow I I YThe code sentence(which is also known to the recipient) is nextwritten by him upon a pador elsewhere' with, thecypher beneath it thus AdelaideT.v

Fra

The slide member 3 is then moved to bring ythe F upon it adjacent the Aon-the base The letter N willy nowappear in member I. the window II andforms the rstletter of the message.,Y fr, f

The slide'memberA 3 is next movedv to bring the Rfupon it adjacent the Don theslide member. This brings the letter E into'k the lwindowformingthe'secondv letter of the message.

Similarlyl when the A of the Yslide member 3 is brought adjacent the Eon the base member -I the letter W will appear in the'window forming thethird letter-of the message.

instrument is*V 'Deciphering is effected in the. fuewig man'- We thushave the beginning of the message New In the above described instrumentI have shown the letters upon the members in correct alphabetical order,which sequence is preferable but which ris not indispensable. The orderof the letters must however, for the above described mannerV of usingthe instrumenm` be the same on each of the members. .Y c

I have shown the alphabetduplicated upon the base member I but this isonly for convenience of operation and in many cases reduces theextent-ofmovement of theslide member 3, for example'to move the sliderso that the N comes adjacent the Z instead of adjacent the A as shown inFig. 1 it is onlynecessary to move through one space.Y As the lettersare .continuousaround the rotatable memberany particularV letter on theslide member 3 may be associated with anyr particular letter on thebasemember I irrespective -of which alphabet the letteris in, for examplereferring tovFig. l the N on the slide member may be positioned-adjacenteither of the'fAsv on -the'base member, both positionsbringYthe-F-intothe window II.

It is obvious that different 'systems `'of working the instrumentfcanbeformulated butKI prefer the system set forth as by'its use theenciphering anddeciphering isf-earriedf-"o'ut in'thesame manner in eachc ase,'-the code sentence vbeing associated withthe letters upon thebase memberk I, the message to be sent or the message 7(in cypher)received being associated with the slide member 3, and theiresult(thecypher or the encpheredfmessage) being read offfrom the rotatablemember 5 through the window VlrII `'in the base member -I.- Y' `What Iclaim is:` r 5*" 1 An instrument for enciphering and decipheringcomprising, a base member having the letters of the alphabet displayedalong its face, a slide member slidably supported in the base member andhaving the letters ofthe alphabet displayed along its face adjacent theletters upon the base member, a rotatablemembercarriedfuponY a K pin onthe base member, and having the letters of the alphabet upon it, andgearing connecting the rotatable member to the lslide member. 2. Aninstrument according to claim 1icharacterized in that the gearingcomprises, a rack upon lthe slide-'membenfa pinion forming part of thevrotatable member;V and a ratchet and pawl connecting thepihion to theremainder ofthe rotatable member, the pinion. beingy in vengagement withtherack. L f

3. A'n instrument according to clainrl characterized in'that therotatable member ispositioned Within the"bas'e member, and by a'windowin the base-member through which only one letter of the rotatablelmember is visible at' one time. v'

4. An instrument for enciphering and? deciphering comprising, a basememberhavin'g the letters of theY alphabet displayed along its face, aslide member slidablysupported on the base member and having the lettersof the alphabet Ydisplayed along its face adjacent the letters upon thebase member,`l a toothed rack secured to the slide member, a discforming part of `a rotatable member carried upon a pin in the basemember and having the letters ofthe alphabet displayed along its face, apinion forming the other part of lthe rotatable member'supportedcoaxially with the disc and being vin engagement with therack, a ratchet upon the one part of the' rotatable member and a pawlupon the other part of the rotatable member to connect the pinion to thedisc.

5. An instrument according to claim 4 characterized by, a stop buttonupon the base member,

a stop bolt connected therewith, and notches inl the disc one adjacenteach letter thereon, the stop bolt adapted when the stop button isdepressed to engage a notch in the disc and hold the disc.

6. An instrument according to claim 4 characterized by a stop buttonupon the base member, a stop bolt connected therewith adapted when thebutton is depressed to engage notches in the disc of the rotatablemember and hold such disc, a further stop connected to the stop button,a pin `upon the slide member, the stop adapted when the stop button isdepressed to project into the path of the pin to prevent return of theslide member past the zero position.

NORMAN ALEXANDER SMITH. 1o

